Different resorbable materials have been used for the treatment of tissue defects in medicine, with the use of synthetic organic and inorganic materials increasing in the past years. Their advantages are that large amounts of these materials can be rapidly produced, their properties can be tailored according to the clinical requirements and there is no or at least considerably less unwanted immunological reactions compared to autologous tissue transplants.
Several biodegradable polymeric materials have been developed for medical applications. Most materials are polyester derivates, of which polylactide and caprolactone are best documented. These polymers are currently considered as biocompatible, non-toxic materials. Certain polyester copolymers (ε-caprolactone-D, L-lactide) can remain mouldable in low temperatures, which make it possible to inject them into tissue defects as disclosed in WO 99/022011 (Aho et al.).
Also several composites comprising polymer(s) are designed for medical applications in order to improve the contact between the living tissue and the composite. The connection between the composite and the living tissue is normally only mechanical, because the structure of the composite is usually too dense after implantation and does not allow any place for new tissue ingrowth inside the composite material. Therefore, the contact area between the composite and the living tissue is only limited to the contact surface between them. A porous material would solve this problem by providing a larger contact area between the tissue and the material.
Document WO 2002/074356 discloses one possible composite material for use for attaching, growing and repairing of living tissues. The composite comprises a non-expandable matrix polymer and a water-expandable porosity agent. The composite thus comprises a component that, once in contact with body fluids, expands (swells) and breaks the originally continuous phase of the matrix thus exposing the expanded component to the body fluids and reveals the bioactive part of the composite. The voids formed in the composite thereby come into contact with the surrounding tissue.
There remains however still a need to provide an improved material for use as a filler granule in composite materials.